A known radar apparatus includes a light source, a light detector, a polarized light separation element, and a scan element. The light source emits a pulsed laser light. The light detector detects the laser light reflected by an object (also referred to as a reflected laser light). The polarized light separation element is disposed on an optical path of the laser light emitted from the light source, so that the polarized light separation element passes a part of the laser light and reflects another part of the leaser light toward the light detector. The scan element scans the laser light transmitting through the polarized light separation element and reflects the incident laser light toward the polarized light separation element. The radar apparatus measures a distance to an object which reflects the laser light, by measuring a period of time between when the pulsed laser light is emitted by the light source and when the reflected laser light is detected by the light detector (see JP-2789741B).
In the radar apparatus described in JP-2789741B, the scan element scans the laser light, and the polarized light separation element separates the polarized laser light. Thus, the light scanning and the polarized light separating are performed with use of different elements. Therefore, the radar apparatus described in JP-2789741B requires high-accurate adjustment of a positional relationship between the scan element and the polarized light separation element.
JP-2010-70117A describes a vehicle equipped with a radar and an image display device. The radar emits a laser light toward a forward area of the vehicle and receives the reflected laser light to detect an object in the forward area of the vehicle. The image display device emits a beam representing an image to a vehicle compartment to provide information to a driver.
In JP-2010-70117A, an optical system for emitting a laser light to the forward area of the vehicle and an optical system for emitting a laser light to the vehicle compartment are separated. The number of parts in a vehicle system is disadvantageously large.